Abstract
This paper presents a methodology for the development of the bespoke risk-based inspection plan as part of the structural integrity management process of fixed offshore structures for the coast of Brazil. In this context, it is demonstrated how the local components of a jacket structure, e.g., tubular joints, have to be inspected in a way that the risk of global failure is kept under a tolerable level for extreme environmental scenarios as the platform is aging.
The global risk assessment follows a quantitative approach based on the jacket's associated Metocean criteria and actual platform's inspection data to calculate the likelihood of failure mechanisms under Metocean hazard.
In addition, a nonlinear finite element structural model is developed to determine the structural redundancy of the jacket structure under extreme storm events. The outcome of the assessment is required to prioritize the tubular joints which are critical to the redundancy of the structure to keep the structure with reasonably low risk of global failure.
In sequence, probabilistic fatigue calculation is utilized to prioritize inspection resources for the tubular joints which are likely to have fatigue failure during extended service life and, at the same time, represent a significant importance to the probability of failure (pf) of the platform.
The inspection strategy and program, developed in the present study, are focused on the routine underwater inspections, and are based on the recommended practice of the ISO 19901-9 structural integrity management standard.
The methodology is applied for an aged jacket platform in Brazilian waters using the quantitative methodology for RBI plan development. The results of the proposed quantitative risk-based approach are presented to show the advantages of applying a risk-based approach for aged structures.
In this paper, a comprehensive method utilizing software tools available in the market demonstrates how an operator can approach the issue of defining a more effective inspection program towards risk. This method has been applied to aged assets in Brazil making possible for new operators to continue operating safely in brownfields considering an optimized inspection plan based on the most up-to-date industry standards.
